Search Results (1,524)

5052 aluminum alloy has been widely used in aerospace, shipbuilding, automotive, and electronic industries due to its low density, high specific strength, and excellent corrosion resistance. Understanding its laser-induced damage behavior under combined continuous-wave (CW) and nanosecond (ns) pulse laser irradiation is essential for optimizing combined laser processing. In this study, the damage behaviors induced by individual CW laser, individual ns pulse laser, and combined pulse laser were systematically investigated using high-speed imaging, infrared thermography, and three-dimensional surface characterization. The results show that the combined pulse laser significantly enhances both damage depth and material removal efficiency compared with single laser irradiation. Although the peak surface temperature remains nearly unchanged under different processing conditions, the crater morphology and penetration depth vary substantially. High-speed imaging reveals that plasma evolution and molten metal ejection dominate the material removal process. Variations in processing parameters significantly modify molten pool dynamics and plasma behavior. In particular, enhanced plasma shielding or excessive energy dissipation reduces the effective laser energy coupling, leading to decreased material removal efficiency. The synergistic interaction among molten pool evolution, plasma expansion, and molten metal ejection governs the final damage morphology. This study provides new insights into the dynamic interaction mechanisms between combined pulse laser and aluminum alloys, offering guidance for parameter optimization in high-precision laser micromachining. Full article

Ti-6Al-4V titanium alloy is extensively employed in deep-sea structural applications owing to its excellent corrosion resistance, while its extra-low-interstitial (ELI) variant provides higher fracture toughness and is commonly presumed to exhibit even better stress corrosion cracking (SCC) resistance. In this work, displacement-rate-dependent fracture toughness (K_Q) measurements and failure analysis were performed for compact tension specimens machined from an engineering Ti-6Al-4V ELI plate with different orientations, tested in air and 3.5 wt.% NaCl solution over displacement rates of 0.0012–1.2 mm/min. In air, K_Q exhibits a pronounced loading-rate dependence, decreasing by more than 20% at low displacement rates relative to maximum rate, accompanied by quasi-cleavage features on the fracture surfaces indicative of hydrogen-assisted damage, likely arising from environmental or processing-related hydrogen uptake. In 3.5 wt.% NaCl solution, the minimum K_Q within the low-rate regime (0.0012–0.12 mm/min) is 58 MPa·m^0.5, comparable to values reported for conventional Ti-6Al-4V under similar conditions. The pronounced rate dependence and transition toward cleavage-like fracture reveal a strong coupling between loading kinetics and environmental degradation. This work demonstrates that enhanced intrinsic toughness does not necessarily translate into superior SCC resistance and establishes loading rate as a critical factor governing the environmental fracture of Ti-6Al-4V ELI under marine conditions. Full article

Metal corrosion and microbial contamination cause severe damage to marine facilities and result in immeasurable economic losses. Highly efficient and durable anti-corrosion and anti-fouling coatings represent the most effective solution strategy widely employed, whilst two-dimensional graphitic carbon nitride (g-C₃N₄), owing to its non-toxic and highly effective properties, is frequently utilized as a coating filler. Herein, this work innovatively engineered g-C₃N₄ into rod-like structures with layer-oriented alignment through a two-step simplified synthesis process, naturally achieving the self-assembly integration of ultrathin sheets. Subsequently, the special rod-like g-C₃N₄ (RCN) was blended with a polydimethylsiloxane (PDMS) matrix, ultimately yielding a multifunctional nanocomposite coating (RCN/PDMS) that combines mechanical reinforcement, long-term corrosion resistance, and microbial fouling protection. Notably, the compact lamellar structure within uniformly dispersed RCN particles in the polymer matrix effectively enhances the crosslinking density of the composite, significantly improving the coating’s adhesion and tensile strength (1.795 MPa). Furthermore, upon exposure to light, the modified RCN-2 releases substantial reactive oxygen species (ROS), exhibiting pronounced antibacterial activity (90.3% of E. coli and 95.1% of S. aureus) against surface-adhering microorganisms. Following a 60 d marine immersion simulation test, the impedance arc radius of the RCN-2/PDMS coating remained as high as 5.17 × 10⁹ Ω·cm², representing an improvement of nearly two orders of magnitude over pure PDMS coatings. This work expands the application of morphology-controlled g-C₃N₄-based fillers in marine anti-fouling and anticorrosion coatings. Full article

The corrosion behavior of N80 steel in a simulated coalbed–methane environment was investigated in a high-temperature, high-pressure autoclave. Uniform corrosion and maximum pit depth were quantified by weight-loss measurements and ultra-depth-of-field three-dimensional microscopy, respectively, while SEM, EDS, and XRD were used to characterize the morphology, elemental composition, and crystalline phases of the surface corrosion products. A one-factor-at-a-time design was applied at a constant total pressure of 10 MPa to evaluate the effects of nominal CO₂ partial pressure (0.10–1.00 MPa), nominal O₂ partial pressure (0–0.40 MPa), Cl⁻ concentration (3–187 g/L), and temperature (40–75 °C). Increasing the nominal CO₂ partial pressure raised the uniform corrosion rate from 0.712 to 0.930 mm/a but reduced the maximum pitting corrosion rate from 1.691 to 0.280 mm/a, while FeCO₃-containing surface coverage increased. Increasing the nominal O₂ partial pressure intensified both corrosion modes; at 0.40 MPa, the uniform and maximum pitting corrosion rates reached 1.446 and 2.202 mm/a, respectively, and the corrosion-product layer exhibited extensive cracking and spallation. Increasing the Cl⁻ concentration reduced the uniform corrosion rate from 1.078 to 0.839 mm/a but increased the maximum pitting corrosion rate from 0.474 to 1.807 mm/a, indicating a shift in the principal damage risk from average metal loss to localized penetration. The uniform corrosion rate reached a maximum of 1.516 mm/a at 60 °C, whereas the maximum pitting corrosion rate increased continuously to 2.202 mm/a at 75 °C. XRD identified Fe, FeCO₃, Fe₂O₃, Fe₃O₄, and FeOOH. The persistent Fe substrate reflections, interpreted together with the SEM observations, revealed spatially heterogeneous corrosion-product coverage. These results show that the protective contribution of FeCO₃-containing products depends on their surface coverage and visible integrity rather than on phase presence alone. The findings support stringent oxygen-ingress control, targeted pitting protection in high-salinity environments, and enhanced corrosion surveillance of intermediate- and high-temperature well sections. Full article

High-strength steel has attracted increasing attention in civil engineering because of its high strength-to-weight ratio and potential for material-efficient design. This narrative review, supported by a structured literature search, summarizes recent advances in the material behaviour, durability and structural performance of high-strength steel. The discussion covers constitutive behaviour, fatigue and fracture, corrosion degradation, high-temperature and post-fire properties, residual stresses, structural members and connections. Existing studies show that increasing steel strength is commonly accompanied by reduced ductility and strain-hardening capacity, while local buckling, residual stress, welding-induced heterogeneity, fatigue damage, corrosion and thermal degradation remain important design concerns. The accuracy of current design provisions varies with steel grade, product form, section geometry, failure mode and exposure condition, and direct extension from conventional steels is not always appropriate. Future research should emphasize coupled degradation mechanisms, consistent material characterization, broader experimental validation and design models with clearly defined applicability limits. Full article

This study investigates the time-dependent seismic fragility of reinforced concrete (RC) bridge piers exposed to the harsh saline–alkali environments of Northwest China. A comprehensive analytical framework was developed by integrating quasi-static cyclic tests, nonlinear finite element modeling, and incremental dynamic analysis (IDA). Four pier specimens were subjected to accelerated corrosion in a composite sulfate–chloride solution for up to 90 days. Experimental results reveal a critical threshold: once the actual mass loss of the longitudinal reinforcement reaches approximately 12.05% (corresponding to a stirrup mass loss of approximately 21.45%), the severe loss of core confinement triggers a fundamental failure mode transition from ductile flexural yielding to brittle flexural-shear failure. Traditional displacement-based parameters are fundamentally inadequate for capturing this brittle shift; therefore, the Krätzig hysteretic energy dissipation index was adopted to rigorously quantify structural damage. Subsequently, a time-dependent Probabilistic Seismic Demand Model (PSDM) was constructed, explicitly incorporating the experimentally calibrated reinforcement degradation laws. The fragility analysis demonstrates a distinct biphasic degradation mechanism: while short-term sulfate attack temporarily enhances initial stiffness via a “pore-filling effect,” prolonged composite exposure drastically amplifies seismic vulnerability. Notably, under a severe earthquake intensity of 1.0 g (PGA), the exceedance probability for Severe Damage reaches 50.24% after 90 days of exposure, representing a 2.7-fold increase compared to the uncorroded baseline This research provides a robust, energy-based quantitative methodology for the lifecycle seismic evaluation and maintenance of transport infrastructure in aggressive composite environments. Full article

Due to their high strength-to-weight ratio and corrosion resistance, carbon fiber-reinforced polymers (CFRPs) are increasingly used as tension elements in bridge engineering. Their pronounced anisotropy, resulting from stiff carbon fibers and a weaker polymer matrix, is critical for fatigue behavior under multiaxial dynamic stress states, such as those occurring in stay cables over saddles of extradosed bridges or at clamps of suspension-bridge hangers. This multiaxial loading can cause progressive damage accumulation in the contact regions and lead to premature failure. To study this efficiently, an energy-based progressive damage analysis (PDA) model for CFRP tension elements under multiaxial fatigue loading was implemented as a vectorized user material in ABAQUS^® 6.14 (VUMAT in FORTRAN) and validated against tension-tension fatigue tests on pin-loaded CFRP straps. The model was then applied to two representative bridge applications, viz. a clamped CFRP rod and a CFRP cable bent over a saddle, where parameters such as clamping pressure, maximum stress level, and friction coefficient were varied to quantify their influence on fatigue life and to assess suitability in line with fib recommendations. The results indicate that clamping pressures inducing transverse compressive stresses above roughly 85% of the CFRP’s transversal compressive strength significantly reduce fatigue life, whereas keeping the maximum fatigue stress below about 40% of the mean longitudinal tensile strength, the stress amplitude below 200 MPa, and the friction coefficient near 0.2 yields fatigue lives exceeding 2 × 10⁶ load cycles, which is satisfactory under fib criteria. Full article

Accidental web openings caused by impact, corrosion, or conflict-related damage can substantially reduce the strength, stiffness, and stability of steel bridge girders. Although numerous studies have examined beams containing intentionally designed web openings, limited experimental research has systematically compared practical rehabilitation methods for accidental openings in slender-web plate girders. This study experimentally and numerically evaluates several rehabilitation configurations incorporating welded patch plates and transverse stiffeners. Ten slender-web steel girder specimens, each 1800 mm long, 800 mm deep, and 300 mm wide, were tested under monotonic concentrated loading at mid-span. Nonlinear finite element models were also developed to qualitatively examine the principal deformation and instability trends. Relative to the control specimen, the untreated web opening reduced the ultimate load by approximately 43% and exhibited approximately 10% greater deflection at its respective ultimate load. One-sided and two-sided welded patch plates increased the ultimate load of the damaged specimen by approximately 22% and 26%, respectively. Transverse stiffeners increased the ultimate load by approximately 73% while exhibiting substantially lower ultimate-load deflections. The combined use of patch plates and transverse stiffeners provided the greatest improvement, increasing the ultimate load by approximately 101–123% relative to the untreated damaged specimen and substantially reducing lateral instability. The findings demonstrate that effective rehabilitation of slender-web girders requires not only restoration of the interrupted load path but also restraint of web instability. Full article

Rapid corrosion and poor coating adhesion continue to limit the use of magnesium alloys as temporary orthopedic implants. The two-stage laser process was developed to separate the high-temperature melting of 45S5 bioactive glass (BG) from the low-melting-point AZ31 substrate. Femtosecond-laser grids with spacings of 100, 200, and 300 μm were first produced on AZ31 to provide anchoring sites. Then, the target 45S5 BG was suspended above the substrate, locally melted with CO₂ laser, and transported onto the textured surface by gas jet. The 200 μm grid texture for Mg substrate with lowest water contact angle could give the highest tape-test adhesion rating (4B). At the selected deposition conditions of 20 W and 20 L·min⁻¹, two coating cycles produced a continuous layer approximately 50.5 μm thick. Relative to bare Mg alloy, this double-layer coating increased polarization resistance from 1.20 × 103 to 1.39 × 10⁵ Ω·cm² and decreased corrosion current density from 8.70 × 10⁻⁴ to 5.33 × 10⁻⁶ A·cm⁻². It also limited alkalization and mass loss during 28 days in simulated body fluid. As such, the double-layer surface coating supported apatite formation and improved MC3T3-E1 proliferation and alkaline phosphatase activity. These findings indicated that suspended-target deposition was able to form adherent, bioactive glass coatings on magnesium while limiting direct thermal damage to the substrate. Full article

This study investigates the structural behavior of steel I-beams containing corrosion-induced section loss and web openings, along with the effectiveness of fiber-reinforced polymer (FRP) strengthening as a retrofit strategy. Although previous studies have investigated the effects of corrosion, web openings, and FRP strengthening in steel beams, limited attention has been given to comparing the structural response of slender and deep steel beams under these deterioration scenarios and assessing strengthening strategies according to their distinct failure mechanisms. The analysis considers two structural response regimes: slender beams governed predominantly by flexural behavior and deep beams where shear deformation plays a significant role. Three-dimensional (3D) nonlinear solid finite element (FE) models are developed to evaluate the influence of corrosion location, web opening position, and FRP-strengthening schemes on load-carrying capacity and failure behavior. The results indicate that corrosion-induced flange thinning significantly reduces flexural capacity in slender beams, while web degradation has a comparatively smaller effect. FRP strengthening of the tension flange is found to be the most effective strategy for restoring flexural performance in slender beam configurations. In contrast, deep beams exhibit higher sensitivity to shear-related damage, where web openings located in shear transfer regions lead to substantial reductions in load capacity. Strengthening of the web region using FRP significantly improves shear resistance and overall structural performance. Overall, the study highlights distinct differences in damage sensitivity and strengthening effectiveness between slender and deep beam responses under corrosion and web opening effects, providing practical guidance for condition assessment and retrofit design of deteriorated steel I-beams. Full article

The rapid development of implantable medical electronics requires robust biocompatible coatings capable of ensuring long-term stability in aggressive physiological environments. Although Grade 1 titanium is widely used for its excellent mechanical properties and corrosion resistance, active implants require defect-free insulating coatings to prevent electrical leakage and metal ion release. This study presents a systematic evaluation of Parylene C (P-C) thin films deposited by the Gorham chemical vapor deposition (CVD) process onto implant-grade titanium substrates. Four coating thicknesses (1, 5, 10, and 20 µm) were deposited and characterized using complementary chemical, morphological, optical, and mechanical techniques. Contact-angle measurements confirmed uniform hydrophobicity (90.56 ± 1.86°), while FTIR and EDX verified the characteristic chemical composition of P-C. Reflectometry, ellipsometry, and interferometry demonstrated excellent thickness control and deposition reproducibility. Pull-off testing showed high initial mechanical integrity, with detachment forces ranging from 52 to 73 N. However, accelerated PBS ageing (21 days at 90 °C) induced significant degradation, particularly for thicker coatings, reducing pull-off forces to 19–42 N. Likewise, thermal-shock cycling (−80 °C to +220 °C) caused severe interfacial damage, decreasing the required detachment force to approximately 5.5 N for 20 µm coatings because of extensive cracking and delamination. These results demonstrate that Parylene C provides excellent conformal coverage and chemical stability on titanium but that its durability is significantly affected by prolonged hydrothermal ageing and extreme thermal loading. This study provides practical guidelines for the design of reliable encapsulation systems for active implantable medical devices and highlights the need for improved interfacial engineering through optimized adhesion-promoting layers or hybrid protective architectures. Full article

This paper investigates the stress corrosion cracking (SCC) behavior under constant loading conditions and the early-stage grain-scale deformation mechanisms of a friction-stir-welded (FSW) joint of 7A52 aluminum alloy. The results show that when a constant load equivalent to 1.0 times the yield strength (439.43 MPa) of the base metal is applied, the joint fractures after 72 days of immersion in a 3.5 wt% NaCl solution, with the fracture located in the heat-affected zone on the advancing side (AS-HAZ). The fracture surface exhibits a mixed-mode morphology characterized by both brittle and ductile features. Observations suggest that cracks mainly initiate at the bottom of corrosion pits, at grain boundaries, and at the interfaces between precipitates (such as Mg-Si-rich, Al-Fe-rich, or Al-(FeMn)-rich) and the Al matrix. It is suggested that the initiation mechanisms are closely related to galvanic corrosion, interfacial weakening, and mechanical property mismatch. In situ tensile and EBSD results indicate that the AS-HAZ is the first region to undergo deformation. As the load increases from 400 N to 1500 N, the degree of strain localization intensifies, with high-strain regions preferentially concentrated at grain boundaries. Grain boundary damage is likely a key mechanism responsible for the initial failure on the advancing side of the FSW joint. Further in situ SEM observations reveal that during the early stage of tensile deformation, as the load increases from 300 N to 455 N, the grain surface in the AS-HAZ evolves from a flat morphology to a typical orange peel appearance. Meanwhile, grain boundaries change from clearly visible to blurred, slip traces increase, and multiple slip systems are activated within the grains. The continuous pile-up of dislocations at grain boundaries leads to a sharp increase in local stress concentration, ultimately inducing grain boundary instability and crack nucleation. Full article

The corrosion performance of Al-Mg-Si-Cu laser–arc hybrid welded joints modified by 1.8 wt.% Ni remains poorly clarified. In this study, the corrosion behavior was examined via electrochemical measurements combined with SEM, EDS, and SKPFM. Nickel alloying increased the corrosion potential of the α-Al matrix above that of eutectic Si, thereby suppressing the cathodic role of eutectic Si. Nevertheless, the pronounced potential difference and extensive interfacial area between the Al₃Ni phase and the α-Al matrix promoted localized galvanic corrosion, resulting in chain-like pits along the Al₃Ni phase. This intense galvanic coupling considerably damaged the compactness of the passive film and reduced its resistance. Consequently, the corrosion current density of the welded joint increased significantly from 0.83 μA/cm² to 1.85 μA/cm². These findings suggest that Ni alloying is suitable for welding Al-Mg-Si-Cu alloys in applications where high mechanical performance is essential and corrosion resistance is of secondary importance, such as in body-in-white or chassis load-bearing components. Full article

AISI 316L austenitic stainless steel is extensively used in petrochemical storage and processing equipment because of its excellent corrosion resistance. However, exposure to concentrated hydrochloric acid severely destabilizes its passive film, promoting active dissolution and localized corrosion. This work investigates the corrosion behavior of AISI 316L stainless steel in hydrochloric acid solutions of 7.2, 9.6, and 12 M at room temperature. Cyclic potentiodynamic polarization (CPP) tests were performed according to ASTM G61, and the corrosion morphology was characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and metallographic cross-sections. The electrochemical results revealed an active dissolution regime characterized by the absence of a stable passive region and positive hysteresis loops in all HCl solutions, indicating irreversible surface damage and poor repassivation. The corrosion current density increased from the order of 10⁻¹ mA cm⁻² in 7.2 and 9.6 M HCl to the order of 10¹ mA cm⁻² in 12 M HCl, demonstrating a significant acceleration of the corrosion kinetics. SEM and cross-sectional analyses confirmed the development of localized pitting corrosion, with pit depths reaching approximately 0.87 mm. The results demonstrate that concentrated hydrochloric acid promotes the coexistence of generalized active dissolution and localized pitting corrosion, while increasing HCl concentration modifies the morphology and propagation mode of the pits. Full article

Deoxidized high-phosphorus (DHP) copper is widely used in marine heat-exchangers and seawater piping, where long-term structural reliability demands both high strength and a deformation-tolerant microstructure to resist damage initiation. Constrained groove pressing (CGP) is a scalable severe plastic deformation route for metallic sheets; however, the sharp trapezoidal junctions of the conventional die impose parasitic bending strains that produce sinusoidal in-plane hardness variations and anisotropic properties. This study introduces a modified CGP (MCGP) process in which the sharp crest and valley of each 45° tooth are replaced by tangent circular arcs (R₁ = 1.6 mm at the crest, R₂ = 4.8 mm at the valley), removing geometric discontinuities while exactly preserving the groove angle, pitch, and die envelope for drop-in compatibility with existing equipment. DHP copper sheets processed by conventional CGP and MCGP were systematically compared using optical microscopy, SEM, XRD, microhardness, tensile testing, and finite-element analysis. MCGP delivered exceptional mechanical performance: yield strength of 281.19 MPa, ultimate tensile strength of 451.94 MPa (96.4% above the as-received state and 23.8% above conventional CGP), mean hardness of 131.38 HV, and the finest apparent (instrument-uncalibrated) coherent diffraction-domain size of 22.75 nm. Finite-element modelling revealed a lower peak equivalent plastic strain with a more continuously distributed through-thickness deformation path, despite an unchanged nominal grooving strain (≈0.56). Notably, while the modified die redistributes deformation rather than amplifying the nominal strain, the measured through-thickness hardness inhomogeneity factor increased from 7.14% to 21.97% due to strain concentration in the mid-thickness region, indicating that full homogenisation requires further arc-radius optimisation. Nevertheless, the substantial gains in strength and microstructural refinement demonstrate that MCGP offers a promising processing route for producing DHP copper components with enhanced strength and refined microstructures, which may contribute to improved damage tolerance. However, it is acknowledged that direct tests on seawater corrosion, corrosion fatigue, and thermal cycling were not performed in this study; the implications for marine service life are inferred from the established literature on the benefits of grain refinement for corrosion and fatigue resistance. Future work incorporating marine environmental performance tests is recommended to validate these implications. Full article